More answers

anonymous

7 years ago

it says 62

anonymous

7 years ago

ok, so let's call the tank capacity V (litres), flow rate through large pump F1 and through small pump F2. t1= 100, t2= 160
For pump 1, flow rate F1=V/t1=V/100 (litres/hr)
For pump 2, flow rate F2=V/t2=V/160 (litres/hr)
when 2 pumps run at the same time, we have total flow rate, say F, equal to F1+F2
so F=F1+F2=V/100+V/160=(13V)/800
so the time needed is t = V/F = V/ ((13V)/800)=800/13~61.54~62hrs
hope that clear enough :)

anonymous

7 years ago

Thanks! just one question: how did u get the 13?

anonymous

7 years ago

calculator? lol
1/100+1/160= 8/800+5/800 =13/800

anonymous

7 years ago

oh I understand now. Thanks so much for your help. You're a lifesaver!